My theory is people had their Trek heyday with a particular series and everything after that failed to take. For a lot of folk that was TNG. For others it was the denser politics and arcs of DS9. For some people (now nearly dead) it was TOS.
Not everyone has stamina.
I promise, I SWEAR UPON IDIC that when JJ pops out that teen academy Trek series Star Trek 9021701
I will maintain my love. I will not fail this universe even if it fails me.